This invention relates to tractor trailers and, more particularly, to trailers which are adapted for dismounting the load carrying bed whereby the tractor may be separated and the load bed placed in condition for unloading and/or storage.
Present day tractor trailers of the flatbed type most commonly utilized for freight transportation upon the highways include a tractor having a chassis supported on front and rear wheels and, in turn, supporting a fifth wheel structure upon which a detachable load carrying flatbed is swivelably mounted. The rear end of the load bed is supported by a wheel carriage or bogie thus completing the general structural arrangement of the tractor trailer.
Upon delivery of the load bed with a load supported thereon to a terminal for temporary storage or to the site of a user, the forward end of the load bed is detached from the fifth wheel structure and allowed to rest upon wheels or jacks which are normally pivotally supported underneath the load bed. After detachment of the tractor, the flatbed rests upon the rear bogie and the wheel structure or jacks and in the same plane as the load bed assumed during transportation thereof.
One of the standards of the industry concerns the height of the working level for a flatbed or any other load supporting platform such as freight containers and tanks. The height of this level from the surface of the ground is five feet, and serves as the nominal height to which the trucking industry has accepted and adheres to. This particular height, or any other which the industry may agree to accept, has been dictated by the wheeled bogies, tires sizes, axle load and heights, fifth wheel structure, etc. While this particular height of five feet may be acceptable for accommodating the structure of tractor trailers and for safety reasons on the highway, the height has resulted in flatbeds which are inconvenient with respect to unloading and storage within warehouses and other undercover storage facilities. Conventional trailers, when detached from the tractors and placed in storage areas or areas to be unloaded, include the bogie at the rear end thereof which practice thereby prevents additional use of the bogie until the trailer is unloaded and may be removed from its working area.
Another disadvantage inherent in present day tractor trailer units is that the five foot standardization level limits the number of empty flatbeds which may be placed one upon the other for storage. A piggyback combination of one flatbed and bogie upon another, resulting in a height of approximately ten feet is generally the limit to which these units may be stacked in view of the height of conventional warehouse doorways. This limitation requires the provision of additional warehouse floor space for accommodating still more load beds therein.
In the prior art, a conventional tractor trailer is illustrated and described in U.S. Pat. No. 3,057,499 as including a tractor having a fifth wheel structure mounted thereon, a trailer body having its forward end swivelably connected to the fifth wheel structure, and a rear bogie for supporting during transportation and storage the trailer body. In the illustrated arrangement, the trailer body is adapted for movement onto rail cars for further transportation thereof, the bogie, having been removed from the trailer body prior to placement upon the rail cars. Incident to this arrangement, the tractor trailer includes a bogie lift apparatus which permits the placement of the rear bogie upon the tractor chassis for removal of the same from the working site. In this conventional tractor trailer, the rear bogie would normally remain attached to the trailer body during storage of the trailer or unloading therefrom, thus capturing the bogie and prevent use thereof for further transportation with the tractor. In the event that the trailer body is to remain at a working site for any length of time, the bogie and its tractor will be prevented from further utilization unless additional bogies are in inventory for the trucking concern.
Another conventional form of tractor trailer is illustrated in U.S. Pat. No. 3,070,386 as including a tractor having a chassis supported on front and rear wheels and a rear wheeled carriage for supporting a flatbed thereon in conjunction with a fifth wheel structure mounted on the tractor chassis. As in the above referred to patent, the flatbed of this arrangement is of the conventional height above a road surface upon which the tractor trailer operates.
A tractor trailer has been described in U.S. Pat. No. 4,060,145 which permits the unloading of a very heavy load from a flatbed and placed on support pallets. This permits the removal of the complete tractor trailer so that the same may be utilized for other service while the load may be later unloaded and/or placed in condition for working therefrom. In this arrangement, however, additional pallets must be utilized in conjunction with the flatbed of the truck and the platform of the pallets remain as high as or even higher than the level of the flatbed itself. Lifting structure is associated with the rear bogie of the trailer and the tractor fifth wheel structure so that the flatbed may be lifted along with the pallets during transportation and then lowered to permit the movement of the trailer from underneath the pallet supported thereon.
Another form of demountable transporter associated with tractor trailers is disclosed in U.S. Pat. No. 4,231,709. This arrangement is devised specifically for ISO containers which have been designed and accepted by the industry with standard fittings of a particular configuration for permitting universal handling, such as, transportation hoisting and positioning these containers on container ships, specially designed railroad cars and flatbed trucks. This patent is directed to demountable transporters for attachment to the containers, the transporters including wheels, lifting and lowering mechanism which will permit the transportation of the containers upon the wheels along the highway. While this disclosure is adapted for particular containers, it does not serve the handling of loads which are not contained within these types of containers which in themselves serve as the trailer structure.
In the industry, there are also other arrangements which disclose the structures which will permit the attachment of rear bogies to a tractor chassis for permitting the removal of the moving parts of the tractor trailer to another site for further use thereof. As shown in U.S. Pat. Nos. 2,151,343, 2,296,858, 3,239,237, various arrangements have been illustrated and described which will connect the flatbed having a rear bogie attached thereto to structure associated with the truck tractor.
Therefore, it is the principal object of the present invention to arrange a flatbed associated with a tractor trailer which is detachably related to the tractor chassis and a rear bogie so that the flatbed itself becomes and remains a pallet for the load thereon.
Another object of the invention is to permit the removal of a flatbed with load thereon from a tractor chassis and a rear bogie and to lower the same upon the ground to a height easily accessible to an operator or worker to step up and step down easily without an additional structure.
Still another object of the invention is to utilize the structure which raises or lowers a flatbed from attended tractor structure and rear bogie for use as means for mounting the rear bogie upon the tractor chassis thereby enabling the return of the units to another working site for further use thereof.
The present invention has been devised in order to overcome the disadvantages and problems enumerated above with respect to conventional tractor trailers of the flatbed type. The present invention has been devised for accomplishing the objects by arranging the flatbed so that it becomes a pallet for the load supported thereon, and whereby the pallet has a working level much below the standard level of five feet so that the same may be easily transported within a covered warehouse to a work site whereat workers may easily mount pallet and selectively unload the same. In accomplishing these goals, both the wheel carriages for the tractor and the rear bogie include linkage structure and hydraulic rams for articulating the same for operation to lower the flatbed or pallet from the transporting level thereof of five feet to a significantly lower level. Hydraulic fluid under pressure is conducted to each of the hydraulic ram systems through a path which includes the load bed or pallet so that an operator may raise or lower the pallet and disconnect the same from the respective wheeled units from a remote and single position. The linkage structure for both the rear bogie and the tractor wheel carriage are devised so that the rear bogie may be lifted vertically, and to an inverted position upon the tractor chassis and locked in this position for transporting both carriages to another site.
These and other advantages will become apparent from the following description taken in conjunction with the accompanying drawings wherein: